In an extraction process or reaction process using supercritical fluid or subcritical fluid, various high-pressure generating machines such as pump and compressor are used to bring the fluid into a supercritical or subcritical high-pressure field. The use of such high-pressure machines has problems such as leak of high-pressure fluid, generation of dust from movable parts, and noise. Particularly, the necessity of high-level special knowledge for the maintenance of the high-pressure machines obstructs the application of high-pressure processes to various operations.
Carbon dioxide and water, which are extremely safe materials as fluid, are expected for the application to general operations such as extraction, cleaning, and waste disposal as environmentally suitable materials, but the use of the high-pressure generating machines significantly obstructs the spread of these supercritical fluid processes. Further, the effectiveness of various reactions in supercritical fluid has been found out. However, the use of such high-pressure generating machines obstructs the extension of laboratory research areas.
Further, the pressure condition for operation or experiment is limited depending on the specifications of high-pressure generating machines, which makes a proper condition selection difficult in various aspects. For example, in supercritical carbon dioxide extraction, where an increase in pressure progresses in its operating condition, an extracting operation at 500 atm is becoming mainstream at present, whereas devices lower in pressure than this are mostly used in laboratory. Furthermore, a further increase in pressure is desired for this pressure, and operations at 700 and 1000 atms are also being required.
In the selection of a compressor used for high-pressure operation, the model of compressor is generally determined depending on operating pressure range, fluid flow rate or the like. However, since the kind, flow rate, pressure or the like of fluid in a supercritical or subcritical fluid process is frequently differed from that in a general chemical process, the selection of compressor is not easy. In the process using supercritical fluid where the increase in pressure further progresses as described above, the compressor itself is also often specific, and the selection thereof is one of serious factors in considerations of economical efficiency.
On the other hand, a method using no pump in extraction process and other processes using supercritical or subcritical fluid is proposed (Japanese Patent No. 3079157: Extraction and cleaning system using supercritical fluid as solvent). However, this method asks the drive source for fluid transportation of density difference, and has a limitation in the transfer of a differential pressure in fluid transportation. For example, when a condenser and an evaporator are set to generate the differential pressure by use of the density difference between gas and liquid, a considerable vertical interval must be taken since a head is given by the vertical interval between the condenser and the evaporator, which limits the setting place. Further, the diameter of piping for transportation and fittings such as valve must be determined considering a pressure loss, and a respectable design is required for a large flow rate processing.
Recently, syntheses of various chemical materials such as caprolactam by an instantaneous reaction in supercritical water have been also progressively developed. However, these require that the resident time in a reactor is several seconds or less, and instantaneous cooling to about 100° C. is performed after the end of reaction. In order to realize them, operations almost ignoring economical efficiency have been carried out, including largely excessive supply of high-pressure water preliminarily heated to a reaction temperature or higher to the reactor and further largely excessive supply of cooling water late in the reaction are performed, and such operations have a bad effect on the industrialization.
The present invention thus has an object to provide a system and device for processing supercritical and subcritical fluid capable of efficiently forming a high pressure field in a process using high-pressure fluid such as supercritical or subcritical fluid without using a special compressing device by substantially giving a pressure difference by the state quantity change of the fluid by transfer of only thermal energy.